In Nigeria's arid north these days, it may as well be 2003 all over again. This month, news began to circulate that a recent polio outbreak in the predominantly Muslim region was triggered by a vaccine designed to eliminate it, and it is jarring already raw nerves in the historically volatile setting.

In the summer of 2003, Muslim clerics and disgruntled northern politicians banned polio vaccinations in the area, claiming that the drugs were a Western ploy to spread HIV and sterilize Muslim girls. The year-long mass boycott of the vaccine sparked a rash of new infections, and the virus jumped to about a dozen other countries  a devastating rollback for a polio eradication campaign that seemed finally on the verge of success.

Health workers in Nigeria fear they're on the verge again  of collapse. When the World Health Organization and the Centers for Disease Control revealed in early October that 69 Nigerian children had been paralyzed by polio virus since 2005  and had contracted the illness through exposure to the live virus found in the oral vaccine drop  it was the nightmare situation public health workers had been dreading: the rare vaccine-related outbreak that could spark renewed paranoia and permanently halt eradication efforts.

In the teeming mercantile metropolis of Kano, northern Nigeria's largest city of some 10 million and the epicenter of the 2003 boycott, glittering mosques rise above streets lined with green steel plates bearing scrawled quotes from the Koran, while women hurry past tucked into their hijabs and veils. There's no doubt that Kano is deeply entrenched in Islamic fundamentalism. "Religion is really big here," says Aminu Isa, 32, a taxi driver. "Anything about Islam and the typical Kano man is ready to lose his head."

Anti-Western sentiments run deep here too, fueled lately by a battle between the Nigerian government and U.S. drugmaker Pfizer. In an $8.5 billion lawsuit filed against the company, the Nigerian government says Pfizer caused the deaths of 11 children in Kano as a result of unauthorized clinical trials of an experimental antibiotic for meningitis in 1996  charges that Pfizer denies, but which Islamic leaders have exploited as proof of a conspiracy.

Here, Western education is also seen as a pointedly Christian concept  an apostasy  and literacy levels are virtually nonexistent. "By the time Western education came to Nigeria," says Musa Salisu, 47, an advocate for polio victims in Kano, "most northerners said to anybody agreeing to learn English, 'When you die, you'll enter hellfire.'"

The vaccination ban was officially lifted in September 2004 after tests in
Nigeria and elsewhere proved the vaccine safe, but many Muslim leaders in this region remain at odds with Western health workers  and with the secular federal government, which supports international immunization efforts. Bn Uthman, a radical Muslim cleric, was a vociferous opponent of the polio vaccine four years ago, and was a member of the 13-man body that approved the ban. "We have no regrets," says the revered radical cleric, dressed immaculately in a flowing, white kaftan and a red fez cap, and seated under a flourishing tropical tree outside his Sahaaba mosque in downtown Kano. "Our opposition to the polio vaccine stems from our belief that [it] is harmful to our children.

Despite the clerics' denunciations, however, millions of Nigerian Muslims have come to believe that the boycott was an egregious error of judgment  and eradication campaigns have recently begun recording some encouraging numbers. Health officials say vaccine coverage has doubled countrywide from 35% in 2005 to a high of about 76% in recent months. Rates of new infections have plummeted. "For the first time since 2002, Nigeria does not have the highest number of polio cases globally," says Christine Jaulmes, UNICEF spokeswoman in Nigeria. "There was an overall 80% decline in the number of children infected with wild polio virus between January and August 2007 compared with the same period in 2006" (when Nigeria accounted for 1,125 of the 2,000 polio cases reported worldwide), going from 945 cases during that period in 2006 to only 198 cases so far this year.

Why the change? For starters, the Polio Immunization Plus Initiative started packaging the polio vaccine with lots of other enticing goods: vaccinations against measles, whooping cough, diphtheria and hepatitis, along with insecticide-treated mosquito bed nets, de-worming medicine and vitamin A supplements. Meanwhile, better-targeted vaccines helped bring the most virulent strains of the disease under control. "For the past one year, we have not recorded a single case of polio type 1 or 11, which are the most dangerous, and we believe we will get rid of polio," says Abdurrahman Yakubu, the Kano state immunization coordinator. "As of September this year, we recorded only 50 polio cases in Kano, compared with 357 in the same period last year."

Perhaps equally as remarkable as these successes are the declarations of support from powerful northern politicians  and even from some Muslim clerics. "The campaign to eradicate the polio virus must be intensified," says Sheikh Ahmed Gumbi, the powerful chief imam of the Sultan Bello mosque in Kaduna [Nigeria's second largest northern city]. "The good job must be completed. The vaccine is safe and healthy, despite a few cases of vaccine-induced infections. The immunization should continue until Nigeria is polio free."

Statements like this go a long way toward fostering trust within the community. "Now we are going into [Islamic] schools and vaccinating more children," UNICEF's Jaulmes says. "That would not have happened a few years ago."

Salisu, the advocacy worker in Kano, is well aware of the grief wrought by polio. Salisu was paralyzed by the virus at an early age; his wife is also a polio victim, and so is the couple's four-year-old son, Ibrahim. "Every time I see my son walk on all fours, it breaks my heart," says the father of eight, a quiver in his throat as he sits on a raffia mat outside his modest mud house in the run-down Kuna Asabe neighborhood. Behind Salisu's six-room house is the neighborhood's overflowing refuse dump; an open sewer streams across the property to the dump, swarming with flies and disease.

Born three months before the ban went into effect in 2003, Ibrahim had just one dose of the vaccine the week after he was born. Multiple doses of the vaccine are required for full protection, but Ibrahim couldn't continue because the immunizations were canceled. Ibrahim's legs withered barely a year after the ban was lifted in 2004. When a reporter suggests that his son's affliction could have been caused by the polio vaccine  in rare cases, the weakened virus in the oral vaccine mutates and triggers disease in unimmunized children  Salisu shrugs it off, saying the dangers of refusing the vaccine far outweigh its risks. "Out of, say, one million vaccinated children, only one or a few children end up with vaccine-induced infections," Salisu says, and he is right. "That is a small price to pay to get our children vaccinated."

These days, Salisu works part-time with vaccination teams trying to make inroads in conservative Kano neighborhoods. Perched on his improvised four-wheeled motorbike, Salisu pleads, then cajoles a reticent young mother to allow a health worker to drop a dose of polio vaccine in her year-old daughter's mouth, in front of the family's mud house. "Some parents are still a bit skeptical and need a bit of persuasion," Salisu explains. "I ask recalcitrant mothers whether they want their children to end up crippled like me, and then they instantly agree to be vaccinated."

Once again, the eradication campaign seems to have arrived on the eve of success. But, once again, it is in danger of being thwarted by fear and paranoia. And, so far, it seems, there's no official strategy in place to deal with these hurdles. Rather, the de facto plan  to which the Nigerian government and international health officers appear to have tacitly agreed  is not to draw attention to the recent outbreak and to let it quietly go away. Though the outbreak was widely reported in the international media, it is barely mentioned in local papers.

The Nigerian government has consistently declined interviews and issued no formal statements. Pressed for comment, a top Nigerian health official told TIME, "There is no big deal about the whole thing. It is not peculiar to Nigeria." He said, "Our not talking is not because we are hiding anything."

A senior WHO official was equally tight-lipped: "We want to encourage the media to be responsible and to highlight positive information and not blow the issue of VDPV [vaccine-derived polio virus] out of proportion."

Kano's chief health officer, Aisha Kiru, has been fielding a spate of inquiries  mostly from the foreign media  about vaccine-induced infections, despite her best efforts to keep the outbreak under wraps. "Here in Kano, we know what we went through to convince our people to accept the polio vaccine, and now to come and start telling them that children have been paralyzed by the same vaccine that they believe protects their children from paralysis will lead to a mass rejection of the vaccine," Kiru says, her voice rising. "Given the low level of education among our people, it will be a disaster. We will not allow this issue to derail the polio eradication initiative now that we are close to eradicating polio from our society."

The next crucial round of Immunization Plus Days will take place between November 17 and 20. Thousands of men and women in green and white aprons will fan out across the vast region in an effort to vaccinate millions of vulnerable children  experts say the best way to counter the new infections is to intensify the current vaccination effort. Whether or not it works in the far corners of Kano, its effects will surely be borne out around the world.